Django Models

To tackle the above-said problem Django provides something called Django Models.

A Django model is the built-in feature that Django uses to create tables, their fields, and various constraints. In short, Django Models is the SQL of Database one uses with Django. SQL (Structured Query Language) is complex and involves a lot of different queries for creating, deleting, updating, or any other stuff related to the database. Django models simplify the tasks and organize tables into models. Generally, each model maps to a single database table.

This section revolves around how one can use Django models to store data in the database conveniently. Moreover, we can use the admin panel of Django to create, update, delete or retrieve fields of a model and various similar operations. Django models provide simplicity, consistency, version control, and advanced metadata handling. Basics of a model include –

Each model is a Python class that subclasses django.db.models.Model.
Each attribute of the model represents a database field.
With all of this, Django gives you an automatically-generated database-access API; see Making queries.

Syntax:

from django.db import models       
class ModelName(models.Model):
       field_name = models.Field(**options)

Example:

Python3

# import the standard Django Model 
# from built-in library 
from django.db import models 
from datetime import datetime 
  
class GeeksModel(models.Model): 
  
    # Field Names 
    title = models.CharField(max_length=200) 
    description = models.TextField() 
    created_on = models.DateTimeField(default=datetime.now) 
    image = models.ImageField(upload_to="images/%Y/%m/%d") 
  
    # rename the instances of the model 
    # with their title name 
    def __str__(self) -> str: 
        return self.title

Whenever we create a Model, Delete a Model, or update anything in any of models.py of our project. We need to run two commands makemigrations and migrate. makemigrations basically generates the SQL commands for preinstalled apps (which can be viewed in installed apps in settings.py) and your newly created app’s model which you add in installed apps whereas migrate executes those SQL commands in the database file.

So when we run,

Python manage.py makemigrations

SQL Query to create above Model as a Table is created and

Python manage.py migrate

creates the table in the database.

Now we have created a model we can perform various operations such as creating a Row for the table or in terms of Django Creating an instance of Model. To know more visit – Django Basic App Model – Makemigrations and Migrate.

Now let’s see how to add data to our newly created SQLite table.

Django CRUD – Inserting, Updating, and Deleting Data

Django lets us interact with its database models, i.e. add, delete, modify and query objects, using a database-abstraction API called ORM(Object Relational Mapper). We can access the Django ORM by running the following command inside our project directory.

python manage.py shell

Adding objects

To create an object of model Album and save it into the database, we need to write the following command:

Python3

from gfg_site_app.models import GeeksModel 
  
obj = GeeksModel(title="w3wiki", 
   description="GFG is a portal for computer science students") 
obj.save()

Retrieving objects

To retrieve all the objects of a model, we write the following command:

Python3

GeeksModel.objects.all()

Output:

<QuerySet [<GeeksModel: w3wiki>]>

Modifying existing objects

We can modify an existing object as follows:

Python3

obj = GeeksModel.objects.get(id=1) 
obj.title = "GFG"
obj.save() 
  
GeeksModel.objects.all()

Output:

<QuerySet [<GeeksModel: GFG>]>

Deleting objects

To delete a single object, we need to write the following commands:

Python3

obj = GeeksModel.objects.get(id=1) 
obj.delete() 
  
GeeksModel.objects.all()

Output:

(1, {'gfg_site_app.GeeksModel': 1})

<QuerySet []>

Refer to the below articles to get more information about Django Models –

Python Web Development With Django

Python Django is a web framework that allows to quickly create efficient web pages. Django is also called batteries included framework because it provides built-in features such as Django Admin Interface, default database – SQLite3, etc. When you’re building a website, you always need a similar set of components: a way to handle user authentication (signing up, signing in, signing out), a management panel for your website, forms, a way to upload files, etc. Django gives you ready-made components to use.

Django Models

Python3

Django CRUD – Inserting, Updating, and Deleting Data

Python3

Python3

Python3

Python3

Python Web Development With Django

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